Passat's hot car smells like antifreeze.

It should be caused by water leakage in the heating box.

I suggest you check if antifreeze is missing, and just repair the heater tank.

The function of the warm air tank is to provide heating for the car, raise the temperature inside the car and remove the frost and fog on the window glass. When the engine is working, the coolant heated to high temperature by the combustion of the engine cylinder enters the heat exchanger through the water inlet pipe under the action of the water pump of the engine cooling system, and the heat emitted by the coolant is sent to the carriage or windshield by the air blown by the blower, so as to raise the temperature in the carriage and defrost.